This thesis presents the design, implementation, and validation of a Guidance, Navigation and Control (GNC) system for a lunar rover within a digital twin simulation environment. The main contribution is a unified local navigation architecture in which a single incremental Model Predictive Controller (MPC) serves as an invariant control kernel across two distinct operational scenarios: terrain-aware continuous adaptation and waypoint-based mission execution with hazard avoidance. The rover is modeled as a unicycle kinematic system, and the reference path is represented as an arc length parameterized Piecewise Cubic Hermite Interpolating Polynomial (PCHIP) spline that provides analytical curvature, tangent, and normal vectors at every point.